This invention generally relates to recovering vacuum deposited materials for recycling. More particularly, it relates to apparatus for simplifying the recovery of metals from surfaces of a deposition chamber.
In a vacuum evaporation apparatus, a source material, such as lead, tin, titanium, tungsten, chrome, copper, or gold, is heated in a crucible or on a filament so that the material evaporates. With sufficiently high vacuum, evaporated material moves in a straight line across the chamber, coating all exposed surfaces along the line of sight from the crucible or filament. Both substrates provided in the chamber for coating and chamber surfaces, such as chamber walls or shields, are equally coated.
Semiconductor wafers may be provided in the chamber mounted on a dome designed to hold the wafers at approximately equal distances from the source. In a process in which shadow masks are provided in front of each wafer to provide solder bumps at selected locations on each wafer, the masks are also coated with a large amount of the solder. In such a process less than 1% of the source material evaporated from a crucible may be deposited on areas of the wafer desired as solder bumps. The remaining 99% of the solder coats the mask, spaces on the dome between wafers, shields, and other exposed surfaces within the chamber.
Depending on the thickness of material deposited, the material must be removed from masks, domes, shields and other surfaces after a number of deposition runs have been accomplished. Removal has involved removing and replacing chamber shields and other components or hammering, chiselling, and scraping fixed components. In either case, material removal has taken time from wafer processing. In addition, the removal steps have the potential for exposing workers to hazardous materials, such as lead dust. In addition, once the chamber was cleaned and chamber shields replaced, at least one run without product was needed to ensure that the tool was performing properly. Finally, because the chiselled or scraped material was contaminated by that treatment, it could not be reused in the chamber, and posed a hazardous materials disposal problem. Thus, a better solution is needed that provides a system in which the material that does not coat wafers is more easily removed from chamber surfaces without adding substantially to cost, without reducing throughput, and without providing a hazardous materials problem, and this solution is provided by the following invention.
It is therefore an object of the present invention to provide apparatus that permits easily peeling deposited material from chamber surfaces.
It is a further object of the present invention to provide a method of removing deposited material from chamber surfaces without contaminating the material.
It is a further object of the present invention to provide a method of removing deposited material from chamber surfaces so that the material can be reused without chemical purification.
It is a feature of the present invention that chamber surfaces are coated with Teflon to provide sufficient adherence so that evaporated material adheres but with sufficiently weak adhesion to permit easy peeling.
It is an advantage of the present invention that evaporated lead can be peeled from chamber surfaces rapidly and in large pieces, reducing cost, improving throughput, and reducing human exposure to toxic dust.
These and other objects, features, and advantages of the invention are accomplished by providing a system for depositing material on a substrate. The system includes a chamber comprising chamber surfaces exposed to the deposited material. The system also includes a protective material coating substantially all chamber surfaces, wherein the deposited material adheres to the protective material with sufficient adhesion so the deposited material sticks and wherein the deposited material adheres to the protective material with adhesion sufficiently weak that the deposited material can be peeled off leaving the protective coating in place on the chamber surfaces.